The m3 was driven by a bmw exec for half a year (they give these cars for the executives to drive for a period of time assuming for no fee or a low one),

I am waiting on verification but I think it's safe to assume that it is one of the Advanced Driver Training cars.
4,000 track KM is much different than 4,000 KM driven by an executive. I would hope they are not misleading you because the dealer knows the history of the vehicle.